Protective relay



F eb. 19, 192 9. 1,702,454

v. H. TODD PROTECTIVE RELAY Filed D60. 8, 1925 WH'NESSES: INVENTOR r53 fagmdmn I BYi/I CfOf ATTORNEY Patented Feb. 19, 1929.

UNITED STATES PATENT OFFICE.

VICTOR H. TODD, OF SUMMIT, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

PROTECTIVE RELAY.

Application filed December 8, 1925. Serial No. 74,215.

My invention relates to protective relays tective relay 6 having windings connected to 55 and particularly to reverse-phase or openthe secondary windings of three current phase relays for polyphase systems. transformers 7, 8 and 9 in the respective An object of my invention is to provide phase conductors 10, 11 and 12 of the cir- 5 a relay of the induction type having a movcuit 3.

able armature member and a plurality of The relay 6 comprises a movable armature inductively-related windings for controlling member 15 carrying a contact member 16 the same in case the associated circuit beadapted to cooperate with a stationary concomes unbalanced, one of the phase concuctact member 17 to close the circuit be the i tors or" the circuit is opened or the phase rotrip coil of the circuit-interrupter 4. An

tation of the circuit is reversed. electromagnet 18, a permanent damping 65 In accordance with my invention as apmagnet 19 and a control spring 20 cooperate plied to a three-phase circuit, a relay is proto control the armature member in acvided having a plurality of windings enercordance with the conditions obtaining in 15 gized from three current transformers conthe circuit 3.

nected in the respective phase conductors of The electromagnet 18 comprises a mag- 70 the circuit. netizable core member having three lower The relay comprises four windings, three pole pieces 22, 23 and 24 and two upper opof which are disposed in close proximity to posing pole pieces 25 and 26. Three equal each other on one portion of the magnetizainductively-related star-connected windings ble core member of the relay and the fourth 27 28 and 29 are disposed upon the lower 75 is disposed upon a spaced portion of the core central pole piece 23. A winding 80 that is member cooperating with the first-menwound in opposite directions upon the upper tioned portion to establish a traveling magpole pieces and 26 cooperates with the 25 netic field traversing the relay armature windings 27, 28 and 29 to establish a travelmember under predetermined conditions of ing magnetic field traversing the armature energization of the several windings. The member 15 under predetermined conditions three adjacent windings are connected to the of energization of the respective windings. three current transformers and the fourth The terminals of the star-connected windwinding is so connected to the three other ings 27 28 and 29 are connected to the terwindings that a travelling magnetic field minals of the secondary windings of the S5 in one direction is established under normal current transformers 7 8 and 9, one termibalanced-cu rent conditions in the polynal of: each of the secondary windings of the phase circuit and the field becomes reversed current transformers 7, 8 and 9 being conif the currents become substantially unbalnected together. The winding 30 is connectanced or the current traversing one of the ed in shunt relation to one of the lower-pole phase conductors fails or is reversed. The windings, for instance the winding 29, in fourth winding may be connected to a fitth such manner that the latter winding is travwinding inductively related to the other ersed by a smaller current than the windthree windings, if desired. ings 27 and 28. Therefore, even under bal- For better understanding of my invenanced conditions, when the currents travtion, reference should be had to the accomersing the secondary windings of the transpanying drawings, of which formers 7, 8 and 9 are equal, magnetic fluxes Fig. 1 is a diagrammatic view oi a relay thread the upper and lower pole pieces of 4V embodying my invention as applied to the the electromagnet 18, since the resultant of protection of a three-phase circuit; and the currents in the winding 27, 28 and 29 is 00 Fig. 2 is a similar view of a modified form not zero. of relay embodying my invention. The upper and the lower pole pieces oi The system shown 1n Fig. 1 comprises a the electromagnet 18 are laterally spaced in 50 three-phase alternator 1 connected to a polyorder to establish a traveling magnetic field phase load device 2 through a circuit 3 and in a predetermined direction traversing the a circuit-interrupter 4:. The circuit-interarmature member 15 when the magnetic l is provided with a trip coil 5, the fluxes emanating from the respective sets of enrol? which controlled by pro pole pieces are out of phase The direction of the torque on the armature member depends upon whether the magnetic fluxes from the upper pole pieces and 26 are leading or lagging the resultant fluxes pro duced by the lower pole pieces 22, 23, and 24 traversing the armature member 15.

Under normal conditions when the currents travers' g the phase conductors 10, 11 and 12 are approximately balanced, the currents traversing the respective relay windings 27, 28 and 29 produce a torque upon the armature member of the relay in such direction as to ma rain the con tact members 16 and 17 open. A back-stop and the controlling spring 20 are provided in connection with the armature member 15- to maintain a definite iornial relation between the contact mcmb l6 and 17.

ll one of the phase conductors l0, l1 and 12 becomes open-circuited or the phase rotation of the circuit is reversed, it is desirable to open the circuit-'..iterrupter l to disconnect the load 2. The load 2 may be a polyphrase motor, for instance, that would continue to run si igle-phase if one of the phase conductors of the circuit is interrupted although the motor would overheat under these condition...

If we assume that the phase conductor 10 is open-circuited, the current traversing the winding 27 is reduced and the magnetic flux in the pole energization of the windings 28 and 29 is so modified as to reverse the torque on the armature member 15, thereby closing the contact members 16 and 17 to actuate the circuitinterrupter l. The operation is the same in case either of the phase conductors 11 or 12 is open-circuited or the currents in the respective phase conductors are substantially unbalanced from any cause. Likewise, if any of the phase conductors of the circuit 3 are transposed or the normal phase rotation is reversed in any manner, the energization of the windings 27, 28 and 29 is so modified as to reverse the tprque on the armature member 15 and efi ect the energization of the trip coil 5 of the circuitinterrupter.

In Fig. 2 is shown a modified form of relay in which the windings 27, 28 and 29 are unsymmetrical and the winding 30 is energized througi the instrument-ality of a fifth winding inductively related to the windings 2'7, 28 and 29. The operation of this relay is the same as that described above. Since the windings 27, 28 and 29 are unsymmetrical, having fewer number oi turns than the other windings, a magnetic l'lLlX traverses the pole piece 28 under balanced conditions, thereby energizing the winding 30 to establish normal or restraining magnetic field. The direction of this traveling magnetic field reverses under unbalanced conpiece 23 produced by the' one of the windings 27 ditions, and the relay aru'iature member is actuated to the circuit-closing position.

The relay embodying my invention operates upon a predetermined current rela tion in a polyphase circuit and therefore possesses a considerable advantage over open-phase relays operating upon predetermined voltage relation in the case or" polyphase loads comprising motors. In case 'o't an open phase, such motors will run single-phase and tent to maintain the voltages of the circ substantially balanced although the currents are badly unbalanced.

While I have shown and described in detail a relay that has proven to be extremely sensitive to variations in the normal phase relations of the currents tray ersing a polyphase circuit, I do not consider that my invention is limited to the ecise details shown and described. Many changes in the construction of the electromagnet 20, for instance, without departing from the scope of my invention, will occur to those skilled in the art. 1 do not desire that any iin'iitations shall be imposed upon my in vention therefore except as may be indicated in the appended claims.

I claim as my invention:

1. A protective relay comprising netizable core member having opposed pole pieces separated by an air gap, an armature disposed in said air gap, a plurality of inductively-related windings on one of the pole pieces and a winding on an opposed pole piece connected in shunt relation to one of said firstmentioned windings.

2. A protective relay comprising a movable armature, opposed pole pieces for controlling the movement of said armature, star-connected windings on one of said pole pieces, and a winning on another ct said pole pieces connected in shunt relation to one of said winding.

3. A protective relay comprising a movable armature, two upper and three lower opposed pole pieces for controlling the same, star-connected windings on the central lower pole piece, and a winding for said upper pole pieces energized in accordance with the resultant energization of the first-mentioned windings.

4. A protective relay comprising a movable armature two upper and a lower opposed pole piece for controlling the same a plurality of windings on the lower pole piece and another winding wound in opposite directions on said upper pole pieces and connected in shunt relation to one of said windings on the lower pole piece.

5. A protective relay for a three-phase circuit comprising a movable conducting ara mag two windings ener ing magnetic field traversing said means including to be energized by the third phase conductor of the circuit.

7. A protective relay for a three-phase circuit comprising a movable conducting armature and means for establishing a traveL ling magnetic field normally traversing said armature member in one direction, said means including three current transformers connected in the respective phase conductors of the circuit and a plurality of windings adjacent to the armature member connected to said tran formers and an auxiliary winding arranged to cooperate with said windings to establish a reversed travelling magance with the or rents traversing two phase conductors of the circuit, respectively, and two other windings, one disposed in inductive relation to the firs-at-mentioned windings and the other disposed upon the upper pole pieces of the electromagnet, the said two other wmdings being connected in parallel r if any of the phase conductors of the circuit becomes deenergized.

In testimony whereof, I have hereunto subscribed my name this 17th day of November, 1925.

VICTOR H. TODD. 

